linux-kernel - Re: 3.15-rc2: longhaul cpufreq stalls tasks for 120s+

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Message-ID: <CAKohpo=Lzzj5eki3644-ESB+P39+Q-ARFqN-S+_HM5UB802W3g@mail.gmail.com>
Date:	Thu, 24 Apr 2014 15:59:47 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Meelis Roos <mroos@...ux.ee>
Cc:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel list <linux-kernel@...r.kernel.org>
Subject: Re: 3.15-rc2: longhaul cpufreq stalls tasks for 120s+

On 24 April 2014 15:46, Meelis Roos <mroos@...ux.ee> wrote:
> I can add debug to where needed and try it.

I am quite sure below wouldn't fix it, but just wanted to check
for the corner case :(

Can you please try attached patch (mail's content would be
broken):

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index abda660..7198e23 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -355,10 +355,12 @@ void cpufreq_freq_transition_begin(struct
cpufreq_policy *policy,
                struct cpufreq_freqs *freqs)
 {
 wait:
+       smp_mb();
        wait_event(policy->transition_wait, !policy->transition_ongoing);

        spin_lock(&policy->transition_lock);

+       smp_mb();
        if (unlikely(policy->transition_ongoing)) {
                spin_unlock(&policy->transition_lock);
                goto wait;
@@ -380,8 +382,11 @@ void cpufreq_freq_transition_end(struct
cpufreq_policy *policy,

        cpufreq_notify_post_transition(policy, freqs, transition_failed);

+       smp_mb();
+
        policy->transition_ongoing = false;

+       smp_mb();
        wake_up(&policy->transition_wait);
 }
 EXPORT_SYMBOL_GPL(cpufreq_freq_transition_end);

View attachment "0001-cpufreq-add-smp_mb-s-to-cpufreq-transitions.patch" of type "text/x-patch" (1309 bytes)